#define _CRT_SECURE_NO_WARNINGS 1
#include<iostream>
using namespace std;
const int N = 30;
int n, m, x1, y1;
int a[N][N];
long long dp[N][N];
int main()
{
    cin >> n >> m >> x1 >> y1;
    n++;
    m++;
    x1++;
    y1++;
    dp[0][1] = 1;
    for (int i = 1; i <= n; i++)
    {
        for (int j = 1; j <= m; j++)
        {
            if ((i == x1 && j == y1) || (i != x1 && j != y1 && abs(i - x1) + abs(j - y1) == 3))
                dp[i][j] = 0;
            else
                dp[i][j] = dp[i - 1][j] + dp[i][j - 1];
        }
    }
    cout << dp[n][m];
    return 0;
}